Typically, an inkjet printer is known as a liquid ejection apparatus that ejects liquid from a recording head, or a liquid ejection head, onto a target. The inkjet printer ejects ink (liquid) onto a sheet of recording paper (a target). The printer includes a recording head and a recording paper sheet transport mechanism. The recording head is mounted in a carriage that reciprocates in a main scanning direction. The recording paper sheet transport mechanism transports recording paper sheets in a sub scanning direction. Nozzles are defined in the recording head for ejecting the ink, which is supplied from a cartridge, onto the recording paper sheet. The printer also includes a cleaning mechanism having a cap capable of sealing a nozzle forming surface of the recording head. The cleaning mechanism performs cleaning on the nozzles by drawing the ink from inside the nozzles
Further, a controller of the printer includes a timer device (RTC) that tracks time and a time information memory device (EEPROM), which stores the time at which cleaning has ended as previous end time information. The controller operates the cleaning mechanism to perform cleaning (referred to also as “timer cleaning”) when the difference (or, the elapsed period) between the time tracked by the timer device and the time indicated by the previous end time information, which is stored in the time information memory device, is longer than or equal to a predetermined period (for example, seven days).
The printer has a power supply, or a capacitor, which supplies power to the timer device when the power source of the printer is turned off. Therefore, even when the power source of the printer is deactivated, time tracking by the timer device is sustained as long as the capacitance of the capacitor permits (for example, for four days). However, if the power source of the printer is held in a turned off state longer than the period permitted by the capacitance of the capacitor, supply of the power to the timer device by the capacitor is stopped. The time tracking by the timer device is thus stopped.
To solve this problem, as described in Japanese Laid-Open Patent Publication No. 11-192728, a printer may be connected to an external device such as a host computer. When the power source of the printer is turned on, the printer receives information regarding the current time from the external device and corrects the time tracked by a timer device correspondingly. The time tracked by the timer device of the printer thus becomes substantially accurate. This prevents the timer cleaning from being performed unnecessarily before a predetermined period elapses after the previous cleaning, thus suppressing waste of ink.
Further, as has been recently proposed, a printer may be connected directly to a recording medium, or an external memory, instead of being connected to an external device. The printer executes printing based on printing information stored in the recording medium. When the power source of this printer is turned on, information regarding the current time is not received from the external device. In other words, if time tracking by the timer device has stopped before the power source is turned on, the controller of the printer cannot acquire the current time, as referred to FIG. 10. Accordingly, when the power source is turned on, the timer device must start the time tracking from an initial state and a cleaning mechanism performs cleaning to prevent a defect in ink ejection.
Therefore, without being connected to the external device, the printer of Japanese Laid-Open Patent Publication No. 11-192728 may also perform unnecessary cleaning when the power source of the printer is turned on. Also in this case, excessively repeated cleaning causes undesirable ink loss.